Dental caries is a major oral disease resulting from a complex interaction between the commensal microbiota, host susceptibility (heredity, immunity, diseases, etc.) and environmental factors (diet, dental hygiene, etc.). To predict the patient's risk of new carious lesions or progression of existing lesions, the Caries Risk Assessment (CRA) takes account of clinical, biological and behavioural factors. Thus, the CRA can predict whether the patient is at high or low risk of developing caries. The practitioner can thus set up a follow-up adapted to the risk of the patient. However, although bacteria are the main etiological factor of carious lesions, the CRA does not consider bacterial quantification or just focus on the level of S. mutans in the saliva. As the majority of cavities are interproximal in adolescence, the aim of this trial is to identify and quantify the interdental microbiota of adolescents aged from 15 to 17 years with low or high carious risk. So, the quantification of new biomarkers associated with carious lesion could be added to the CRA to improve it.